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<tr class="t-nv"><td colspan="5"> <strong class="selflink"> Assignment operators</strong>: 
<code>a=b</code>, <code>a+=b</code>, <code>a-=b</code>, <code>a*=b</code>, <code>a/=b</code>, <code>a%=b</code>, <code>a&amp;=b</code>, <code>a|=b</code>, <code>a^=b</code>, <code>a&lt;&lt;=b</code>, <code>a&gt;&gt;=</code>
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<p>Assignment operators modify the value of the object. 
</p>
<table class="wikitable" style="font-size:85%;">

<tr>
<th rowspan="2"> Operator name
</th>
<th rowspan="2"> Syntax
</th>
<th rowspan="2"> Over​load​able
</th>
<th colspan="2"> Prototype examples (for <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> T</span></span>)
</th>
</tr>
<tr>
<th> Inside class definition
</th>
<th> Outside class definition
</th>
</tr>
<tr>
<td> simple assignment
</td>
<td> <code>a = b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"> <small>N/A</small>
</td>
</tr>
<tr>
<td> addition assignment
</td>
<td> <code>a += b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> subtraction assignment
</td>
<td> <code>a -= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy2">-</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy2">-</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> multiplication assignment
</td>
<td> <code>a *= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy2">*</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy2">*</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> division assignment
</td>
<td> <code>a /= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy2">/</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy2">/</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> modulo assignment
</td>
<td> <code>a %= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy2">%</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy2">%</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> bitwise AND assignment
</td>
<td> <code>a &amp;= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy3">&amp;</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy3">&amp;</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> bitwise OR assignment
</td>
<td> <code>a |= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy3">|</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy3">|</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> bitwise XOR assignment
</td>
<td> <code>a ^= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy3">^</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy3">^</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> bitwise left shift assignment
</td>
<td> <code>a &lt;&lt;= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy1">&lt;&lt;=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy1">&lt;&lt;=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td> bitwise right shift assignment
</td>
<td> <code>a &gt;&gt;= b</code>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">Yes
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> T<span class="sy4">::</span><span class="me2">operator</span> <span class="sy1">&gt;&gt;=</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator <span class="sy1">&gt;&gt;=</span><span class="br0">(</span>T<span class="sy3">&amp;</span> a, <span class="kw4">const</span> T2<span class="sy3">&amp;</span> b<span class="br0">)</span><span class="sy4">;</span></span></span>
</td>
</tr>
<tr>
<td colspan="5">
<dl><dd>
<b>Notes</b><br>
</dd></dl>
<ul>
<li> All built-in assignment operators return <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span>, and most user-defined overloads also return <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> so that the user-defined operators can be used in the same manner as the built-ins. However, in a user-defined operator overload, any type can be used as return type (including <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span>).
</li>
<li> <code>T2</code> can be any type including <code>T</code>
</li>
</ul>
</td>
</tr>
</table>
<table id="toc" class="toc"><tr><td>
<div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1">
<a href="operator_assignment.html%23Explanation"><span class="tocnumber">1</span> <span class="toctext">Explanation</span></a>
<ul>
<li class="toclevel-2 tocsection-2"><a href="operator_assignment.html%23Builtin_direct_assignment"><span class="tocnumber">1.1</span> <span class="toctext">Builtin direct assignment</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-3">
<a href="operator_assignment.html%23Example"><span class="tocnumber">2</span> <span class="toctext">Example</span></a>
<ul>
<li class="toclevel-2 tocsection-4"><a href="operator_assignment.html%23Builtin_compound_assignment"><span class="tocnumber">2.1</span> <span class="toctext">Builtin compound assignment</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-5"><a href="operator_assignment.html%23Example_2"><span class="tocnumber">3</span> <span class="toctext">Example</span></a></li>
<li class="toclevel-1 tocsection-6"><a href="operator_assignment.html%23See_also"><span class="tocnumber">4</span> <span class="toctext">See also</span></a></li>
</ul>
</td></tr></table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Explanation">edit</a>]</span> <span class="mw-headline" id="Explanation">Explanation</span>
</h3>
<p><i>copy assignment</i> operator replaces the contents of the object <code>a</code> with a copy of the contents of <code>b</code> (<code>b</code> is not modified). For class types, this is a special member function, described in <a href="as_operator.html" title="cpp/language/as operator">copy assignment operator</a>.
</p>
<p><i>move assignment</i> operator replaces the contents of the object <code>a</code> with the contents of <code>b</code>, avoiding copying if possible (<code>b</code> may be modified). For class types, this is a special member function, described in <a href="move_operator.html" title="cpp/language/move operator">move assignment operator</a>.  <span class="t-mark-rev t-since-cxx11">(since C++11)</span> 
</p>
<p>For non-class types, copy and move assignment are indistinguishable and are referred to as <i>direct assignment</i>.
</p>
<p><i>compound assignment</i> operators replace the contents the contents of the object <code>a</code> with the result of a binary operation between the previous value of <code>a</code> and the value of <code>b</code>.
</p>
<h4>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Builtin direct assignment">edit</a>]</span> <span class="mw-headline" id="Builtin_direct_assignment">Builtin direct assignment</span>
</h4>
<p>For every type <code>T</code>, the following function signatures participate in overload resolution:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span><span class="sy3">&amp;</span> operator<span class="sy1">=</span><span class="br0">(</span>T<span class="sy2">*</span><span class="sy3">&amp;</span>, T<span class="sy2">*</span><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span><span class="kw4">volatile</span> <span class="sy3">&amp;</span> operator<span class="sy1">=</span><span class="br0">(</span>T<span class="sy2">*</span><span class="kw4">volatile</span> <span class="sy3">&amp;</span>, T<span class="sy2">*</span><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>For every enumeration or pointer to member type <code>T</code>, optionally volatile-qualified, the following function signature participates in overload resolution:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy3">&amp;</span> operator<span class="sy1">=</span><span class="br0">(</span>T<span class="sy3">&amp;</span>, T <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>For every pair A1 and A2, where A1 is an arithmetic type (optionally volatile-qualified) and A2 is a promoted arithmetic type, the following function signature participates in overload resolution:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">A1<span class="sy3">&amp;</span> operator<span class="sy1">=</span><span class="br0">(</span>A1<span class="sy3">&amp;</span>, A2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>For expressions E1 of any scalar type <code>T</code>, the following additional forms of the builtin assignment expression are allowed:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td> <div><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span> </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td> <div><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> <span class="br0">{</span>E2<span class="br0">}</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span> </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>Note: the above includes all non-class types except reference types, array types, function types, and the type <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span>, which are not directly assignable.
</p>
<p>The direct assignment operator expects a modifiable lvalue as its left operand and returns an lvalue identifying the left operand after modification. For non-class types, the right operand is first <a href="implicit_cast.html" title="cpp/language/implicit cast">implicitly converted</a> to the cv-unqualified type of the left operand, and then its value is copied into the object identified by left operand.
</p>
<p>When the left operand is a reference type, the assignment operator applies to the referred-to object.
</p>
<p>If the left and the right operands identify overlapping objects, the behavior is undefined (unless the overlap is exact and the type is the same)
</p>
<p>If the right operand is a braced-init-list
</p>
<ul>
<li> the expression <span class="t-c"><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span></span></span> is equivalent to <span class="t-c"><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> T<span class="br0">{</span><span class="br0">}</span></span></span>, where <code>T</code> is the type of <code>E1</code>.
</li>
<li> the expression <span class="t-c"><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> <span class="br0">{</span>E2<span class="br0">}</span></span></span> is equivalent to <span class="t-c"><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> T<span class="br0">{</span>E2<span class="br0">}</span></span></span>, where <code>T</code> is the type of <code>E1</code>.
</li>
</ul>
<p>For class types, this syntax generates a call to the assignment operator with <span class="t-lc"><a href="../utility/initializer_list.html" title="cpp/utility/initializer list">std::initializer_list</a></span> as the argument, following the rules of <a href="list_initialization.html" title="cpp/language/list initialization">list-initialization</a>
</p>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span>
</h3>
<div class="t-example">
<div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw4">int</span> n <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>  <span class="co1">// not an assignment</span>
    n <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>      <span class="co1">// direct assignment</span>
    <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> n <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span>
    n <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>     <span class="co1">// zero-initialization, then assignment</span>
    <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> n <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span>
    n <span class="sy1">=</span> <span class="st0">'a'</span><span class="sy4">;</span>    <span class="co1">// integral promotion, then assignment</span>
    <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> n <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span>
    n <span class="sy1">=</span> <span class="br0">{</span><span class="st0">'b'</span><span class="br0">}</span><span class="sy4">;</span>   <span class="co1">// explicit cast, then assignment</span>
    <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> n <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span>
    n <span class="sy1">=</span> <span class="nu16">1.0</span><span class="sy4">;</span>    <span class="co1">// floating-point conversion, then assignment</span>
    <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> n <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span>
<span class="co1">//    n = {1.0}; // compiler error (narrowing conversion)</span>
 
    <span class="kw4">int</span><span class="sy3">&amp;</span> r <span class="sy1">=</span> n<span class="sy4">;</span>  <span class="co1">// not an assignment</span>
    <span class="kw4">int</span><span class="sy2">*</span> p<span class="sy4">;</span>
 
    r <span class="sy1">=</span> <span class="nu0">2</span><span class="sy4">;</span>       <span class="co1">// assignment through reference</span>
    <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> n <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span>
    p <span class="sy1">=</span> <span class="sy3">&amp;</span>n<span class="sy4">;</span>      <span class="co1">// direct assignment</span>
    p <span class="sy1">=</span> nullptr<span class="sy4">;</span> <span class="co1">// null-pointer conversion, then assignment </span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">1 0 97 98 1 2</pre></div></div> 
</div>
<h4>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Builtin compound assignment">edit</a>]</span> <span class="mw-headline" id="Builtin_compound_assignment">Builtin compound assignment</span>
</h4>
<p>For every pair A1 and A2, where A1 is an arithmetic type (optionally volatile-qualified) and A2 is a promoted arithmetic type, the following function signatures participate in overload resolution:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">A1<span class="sy3">&amp;</span> operator<span class="sy2">*</span><span class="sy1">=</span><span class="br0">(</span>A1<span class="sy3">&amp;</span>, A2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">A1<span class="sy3">&amp;</span> operator<span class="sy2">/</span><span class="sy1">=</span><span class="br0">(</span>A1<span class="sy3">&amp;</span>, A2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">A1<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span>A1<span class="sy3">&amp;</span>, A2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">A1<span class="sy3">&amp;</span> operator<span class="sy2">-</span><span class="sy1">=</span><span class="br0">(</span>A1<span class="sy3">&amp;</span>, A2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>For every pair I1 and I2, where I1 is an integral type (optionally volatile-qualified) and I2 is a promoted integral type, the following function signatures participate in overload resolution:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">I1<span class="sy3">&amp;</span> operator<span class="sy2">%</span><span class="sy1">=</span><span class="br0">(</span>I1<span class="sy3">&amp;</span>, I2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">I1<span class="sy3">&amp;</span> operator<span class="sy1">&lt;&lt;=</span><span class="br0">(</span>I1<span class="sy3">&amp;</span>, I2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">I1<span class="sy3">&amp;</span> operator<span class="sy1">&gt;&gt;=</span><span class="br0">(</span>I1<span class="sy3">&amp;</span>, I2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">I1<span class="sy3">&amp;</span> operator<span class="sy3">&amp;</span><span class="sy1">=</span><span class="br0">(</span>I1<span class="sy3">&amp;</span>, I2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">I1<span class="sy3">&amp;</span> operator<span class="sy3">^</span><span class="sy1">=</span><span class="br0">(</span>I1<span class="sy3">&amp;</span>, I2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">I1<span class="sy3">&amp;</span> operator<span class="sy3">|</span><span class="sy1">=</span><span class="br0">(</span>I1<span class="sy3">&amp;</span>, I2<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>For every optionally cv-qualified object type <code>T</code>, the following function signatures participate in overload resolution:
</p>
<table class="t-dcl-begin"><tbody>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span><span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy2">*</span><span class="sy3">&amp;</span>, <a href="../types/ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span><span class="sy3">&amp;</span> operator<span class="sy2">-</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy2">*</span><span class="sy3">&amp;</span>, <a href="../types/ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span><span class="kw4">volatile</span> <span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy2">*</span><span class="kw4">volatile</span> <span class="sy3">&amp;</span>, <a href="../types/ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span><span class="kw4">volatile</span> <span class="sy3">&amp;</span> operator<span class="sy2">-</span><span class="sy1">=</span><span class="br0">(</span>T<span class="sy2">*</span><span class="kw4">volatile</span> <span class="sy3">&amp;</span>, <a href="../types/ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody></table>
<p>The behavior of every builtin compound-assignment expression <span class="t-c"><span class="mw-geshi cpp source-cpp">E1 op<span class="sy1">=</span> E2</span></span> is exactly the same as the behavior of the expression <span class="t-c"><span class="mw-geshi cpp source-cpp">E1 <span class="sy1">=</span> E1 op E2</span></span>, except that the expression <code>E1</code> is evaluated only once and that it behaves as a single operation with respect to indeterminately-sequenced function calls (e.g. in <span class="t-c"><span class="mw-geshi cpp source-cpp">f<span class="br0">(</span>a <span class="sy2">+</span><span class="sy1">=</span> b, g<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span></span></span>, the += is either not started at all or is completed as seen from inside <span class="t-c"><span class="mw-geshi cpp source-cpp">g<span class="br0">(</span><span class="br0">)</span></span></span>).
</p>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example_2">Example</span>
</h3>
<table class="metadata plainlinks ambox mbox-small-left ambox-notice" style=""><tr>
<td class="mbox-empty-cell"></td>
<td class="mbox-text" style="">This section is incomplete<br>Reason: no example </td>
</tr></table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span>
</h3>
<p><a href="operator_precedence.html" title="cpp/language/operator precedence"> Operator precedence</a>
</p>
<table class="wikitable">

<tr style="text-align:center">
<th colspan="7"> Common operators
</th>
</tr>
<tr style="text-align:center">
<td> <strong class="selflink"> assignment</strong>
</td>
<td> <a href="operator_incdec.html" title="cpp/language/operator incdec"> increment<br>decrement</a>
</td>
<td> <a href="operator_arithmetic.html" title="cpp/language/operator arithmetic"> arithmetic</a>
</td>
<td> <a href="operator_logical.html" title="cpp/language/operator logical"> logical</a>
</td>
<td> <a href="operator_comparison.html" title="cpp/language/operator comparison"> comparison</a>
</td>
<td> <a href="operator_member_access.html" title="cpp/language/operator member access"> member<br>access</a>
</td>
<td> <a href="operator_other.html" title="cpp/language/operator other"> other</a>
</td>
</tr>
<tr style="text-align:center">
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp">a <span class="sy1">=</span> b<br>
a <span class="sy2">+</span><span class="sy1">=</span> b<br>
a <span class="sy2">-</span><span class="sy1">=</span> b<br>
a <span class="sy2">*</span><span class="sy1">=</span> b<br>
a <span class="sy2">/</span><span class="sy1">=</span> b<br>
a <span class="sy2">%</span><span class="sy1">=</span> b<br>
a <span class="sy3">&amp;</span><span class="sy1">=</span> b<br>
a <span class="sy3">|</span><span class="sy1">=</span> b<br>
a <span class="sy3">^</span><span class="sy1">=</span> b<br>
a <span class="sy1">&lt;&lt;=</span> b<br>
a <span class="sy1">&gt;&gt;=</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">++</span>a<br>
<span class="sy2">--</span>a<br>
a<span class="sy2">++</span><br>
a<span class="sy2">--</span></span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">+</span>a<br>
<span class="sy2">-</span>a<br>
a <span class="sy2">+</span> b<br>
a <span class="sy2">-</span> b<br>
a <span class="sy2">*</span> b<br>
a <span class="sy2">/</span> b<br>
a <span class="sy2">%</span> b<br>
~a<br>
a <span class="sy3">&amp;</span> b<br>
a <span class="sy3">|</span> b<br>
a <span class="sy3">^</span> b<br>
a <span class="sy1">&lt;&lt;</span> b<br>
a <span class="sy1">&gt;&gt;</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>a<br>
a <span class="sy3">&amp;&amp;</span> b<br>
a <span class="sy3">||</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp">a <span class="sy1">==</span> b<br>
a <span class="sy3">!</span><span class="sy1">=</span> b<br>
a <span class="sy1">&lt;</span> b<br>
a <span class="sy1">&gt;</span> b<br>
a <span class="sy1">&lt;=</span> b<br>
a <span class="sy1">&gt;=</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp">a<span class="br0">[</span>b<span class="br0">]</span><br>
<span class="sy2">*</span>a<br>
<span class="sy3">&amp;</span>a<br>
a<span class="sy2">-</span><span class="sy1">&gt;</span>b<br>
a.<span class="me1">b</span><br>
a<span class="sy2">-</span><span class="sy1">&gt;</span><span class="sy2">*</span>b<br>
a.<span class="sy2">*</span>b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp">a<span class="br0">(</span>...<span class="br0">)</span><br>
a, b<br>
<span class="br0">(</span>type<span class="br0">)</span> a<br>
<span class="sy4">?</span> <span class="sy4">:</span></span></span>
</p>
</td>
</tr>
<tr>
<th colspan="7"> Special operators
</th>
</tr>
<tr>
<td colspan="7">
<p><a href="static_cast.html" title="cpp/language/static cast"><tt>static_cast</tt></a> converts one type to another compatible type <br>
<a href="dynamic_cast.html" title="cpp/language/dynamic cast"><tt>dynamic_cast</tt></a> converts virtual base class to derived class<br>
<a href="const_cast.html" title="cpp/language/const cast"><tt>const_cast</tt></a> converts type to compatible type with different <a href="cv.html" title="cpp/language/cv">cv</a> qualifiers<br>
<a href="reinterpret_cast.html" title="cpp/language/reinterpret cast"><tt>reinterpret_cast</tt></a> converts type to incompatible type<br>
<a href="../memory/new/operator_new.html" title="cpp/memory/new/operator new"><tt>new</tt></a> allocates memory<br>
<a href="../memory/new/operator_delete.html" title="cpp/memory/new/operator delete"><tt>delete</tt></a> deallocates memory<br>
<a href="sizeof.html" title="cpp/language/sizeof"><tt>sizeof</tt></a> queries the size of a type<br>
<a href="sizeof....html" title="cpp/language/sizeof..."><tt>sizeof...</tt></a> queries the size of a <a href="parameter_pack.html" title="cpp/language/parameter pack">parameter pack</a> <span class="t-mark-rev t-since-cxx11">(since C++11)</span><br>
<a href="typeid.html" title="cpp/language/typeid"><tt>typeid</tt></a> queries the type information of a type<br>
<a href="noexcept.html" title="cpp/language/noexcept"><tt>noexcept</tt></a> checks if an expression can throw an exception <span class="t-mark-rev t-since-cxx11">(since C++11)</span><br>
<a href="alignof.html" title="cpp/language/alignof"><tt>alignof</tt></a> queries alignment requirements of a type <span class="t-mark-rev t-since-cxx11">(since C++11)</span>
</p>
</td>
</tr>
</table>

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